Birdsare flight orientated organisms.
Each part of its anatomy is modified in some way to allow it to
keep its body light and energetic for flight.

Very active metabolism. They can eat, digest,
and eliminate the waste in a short amount of time. Their body
temperature is rather high 102-103 degrees F. They are
endotherms.

They contain a four chambered heart.

Their skeleton is constructed of light weight
bones supported by an inner meshwork of bony material to give
extra support while flying.

The female loses one of its ovaries.

They have no teeth and their beak is made of a
light protein keratin.

They contain feathers, also made of keratin.
There are three types of feathers: down feathers which are
used for insulation, contour feathers which are colorful
and used for recognition, and keeping the body aerodynamic, and
quill feathers which are used for flight . These feathers
are lost periodically (molting).

They have an extensive air sac system attached
to the lungs. This reduces the weight of the bird and supplies the
needed air for a fast metabolism. It also is used to dissipate the
tremendous amount of heat built up from metabolism.

They develop from the amniote egg. Bird egg
shells are hardened with calcium carbonate for added
protection.

Birds that are ready to carry on life's duties
upon hatching are called precotial, while those that need further
development are called altricial.

They have a well developed nervous system.
Acute vision, and external ears.

Well developed muscles. The keel ,a part of the
sternum, allows large pectoral muscles to be attached to the
skeleton.

Their forelimbs are modifies as wings. These
wings are homologous to the limbs of the reptiles, amphibians, and
mammals.

Their hind limbs are modified for various jobs
based on the structure of their claws.

Birds are an excellent indicator of the fitness
of the environment. They help keep the insect population down, use
rodents as a food source, help rid the environment of dead and
decaying organic material, and help pollinate many types of
plants.

Many birds migrate over long distances to find
suitable breeding grounds and protection from major climatic
changes.